Analysis of Ultra-Low Frequency Oscillation in Southwest Power Grid Based on Measurement Data

The ultra-low frequency oscillation (ULFO) is found in the future Southwest Power Grid under some faults, which will asynchronous interconnect with the State Grid via the HVDC and VSC-HVDC at the end of the 2018. This paper introduces the phenomenon of ultra-low frequency oscillation of asynchronous interconnection in Southwest Power Grid and analyzes the characteristics of ultra-low frequency oscillation with measurement data. In details, the energy flow calculated with the measure data is used to evaluate the contribution of each unit to the ultra-low frequency oscillation and locate disturbance sources of the oscillation. Meanwhile, the amplitude-phase characteristic for the oscillation at the different power plant is used to identify that the oscillation is mainly manifests between the hydropower units and the thermal power units. Furthermore, the damping characteristics of the excitation and governor system analysis reveals that the main factor of the oscillation is the lack of the damping or negative damping characteristic of the hydro-turbine governor systems.